Serum biomarkers of inflammation for diagnosis of prostate cancer in patients with nonspecific elevations of serum prostate specific antigen levels

Background: Lactate dehydrogenase (LDH) and C-reactive protein (CRP) are biomarkers of inflammation commonly used in medicine. The aim was to evaluate the utility of serum LDH and CRP levels for diagnosis of prostate cancer (PC) in men with nonspecific elevations of serum total prostate specific antigen (PSA) levels. Methods: The following serum biomarkers were measured in patients with PSA between 4 and 10 ng/mL: LDH, CRP and free-PSA. The free-to-total serum PSA ratio (%fPSA) was (free-PSA/PSA) x100. Patients were classified into two groups according to diagnosis of prostate biopsy: PC and NOT PC patients. Logistic regression was used for develop a probabilistic model to predict PC patients. Diagnostic accuracy was determined using receiver operating characteristic (ROC) curves, calculating the area under the ROC curve (AUC). Results: We studied 232 patients with ages between 43 and 98 years old (median = 72), 200 NOT PC and 32 PC patients. CRP was not statistically significantl to differentiate between PC and NOT PC patients. Probabilistic model (%) was 100x (1 + e(-Z))(-1); (Z = 0.0070 x LDH -0.1589 x %fPSA -1.4898). The AUCs were 0.657 (P=0.0048), 0.802 (P<0.0001), and 0.844 (P<0.0001) for serum LDH levels, %fPSA values and probabilistic model, respectively. Conclusions: CRP was not useful to differentiate benign from malignant prostate disease, in contrast LDH could be used for diagnosis of PC. A probabilistic model using LDH and %fPSA can improve the diagnostic accuracy in patients with PSA between 4 and 10 ng/mL.